In the manufacture of rectangular filter frames and air filter cells of a V-configuration, a sheet of heavy gauge, wire screen backing is generally secured by sheet metal tabs to the filter frame. A retainer strip is then secured to the frame in some manner such as by riveting or cementing, and an overlying, fibrous filter batt or mat is applied to the retainer strip. The filter mat overlies the wire screen backing to act as a primary filtering media for the incoming air stream. Because these fibrous filter mats must be frequently changed or removed for cleaning purposes, it became necessary to devise an efficient means for easily securing them to and removing them from the structural frames.
To that end, eforts have been made to facilitate the assembly, such as exemplified in the U.S. Pat. to Donachine No. 3,293,834, which discloses a retainer strip having a pair of inwardly and downwardly turned semi-walls which form a slotted front wall into which the edes of the filter mat are secured. In another U.S. Pat. No. 3,470,680, a V-shaped air filter cell utilizes retaning strips having a slotted front wall for gripping the filter mat and a flanged rear wall for securing the retainer strip to the hardware frame. In yet a further U.S. Pat. No. 3,373,546, a specially extruded frame grips a cooperating portion of the retainer strip, but this is very expensive and not easily adapted to V-configuration filter cells.
WHILE THE ABOVE NAMED PATENTS REPRESENT SIGNIFICANT ADVANCES IN THE CONSTRUCTION OF AIR FILTR CELLS, THERE ARE STILL DISADVANTAGES IN CONSTRUCTION TECHNIQUE WHICH DIRECTLY AFFECT THE OVERALL OPERATION THEREOF. One major problem in the construction of rectangular and V-cell filter cells is the necessity for riveting, welding or other sheet metal techniques to secure the structural elements together. In securing the wire screen to the metal frame, it is conventional to form tabs on the frame portion which are bent around the wire mesh to secure it in place. The result is that workmen frequently injure their hands on the metal parts while trying to erect the cells, not only while securing the screen, but also while subsequently working with the fibrous batt thereafter. Further, assembly of the screen and retaining strip to the frame are time consuming, thereby increasing costs.